Testing Against Stored R Objects

Question

Is there a simple workflow to write tests that store objects as .rds or .rda so that future runs of a test can compare the result of code execution vs. the stored object? This would make it easy to check that functions that return somewhat complex values are still behaving as they should.

For example, something like:

test_obj(res <- lm(y ~ x, data.frame(x=1:3, y=5:7)))

which, if *extdata/test_obj.res.rds* doesn't exist, would create it in *inst/extdata/test_obj.res.rds*, with res from above, but if it does exist, would identical/all.equal etc. the newly generated object with the one recovered from the rds.

I would find such tests super useful, and I am a bit surprised that RUnit/svUnit / testthat don't implement something of the sort (I'm hoping they do, and I just haven't found it).

testthat::make_expectation is close, but I'd prefer to have an automated store/retrieve rds rather than copy paste the text representation to a file, which I think is how you're supposed to use testthat::make_expectation (I guess I could pipe stdout() to a .R file, but even then there is a bit of automation that could facilitate the process).

Is this (closed) pull request, https://github.com/hadley/testthat/pull/38/files, what you're looking for? — hadley, Aug 28 '13 at 16:26
Yes, roughly. What did you deem it out of scope for testthat? — BrodieG, Aug 28 '13 at 20:05
A lot of moving pieces, and not obvious how a caching strategy should work. — hadley, Aug 28 '13 at 20:12

score 6 · Accepted Answer · edited May 23 '17 at 11:54

6

It only took me three years, but I wrote unitizer to resolve this issue. It is a unit testing framework with an interactive UI that allows you to review test output and store it / reject it with a single keystroke. It also streamlines the update/test/debug cycle by showing you a proper diff of failing tests, and dropping you into those tests evaluation environments for debugging in the interactive UI.

For example, if we have a matrix rotation function (courtesy @MatthewLundberg) we want to test:

# mx-rotate.R

rotate <- function(x) t(apply(x, 2, rev))

And a script with some tests:

# mx-test.R

mx <- matrix(1:9, 3)
rotate(mx)
rotate(rotate(mx))
rotate(rotate(rotate(mx)))

Then:

library(unitizer)
unitize('mx-test.R')

Will kick-off an interactive session that will allow you to review the results of the three rotation calls and accept them as tests if they work as expected.

There is a screencast demo available.

edited May 23 '17 at 11:54

Community

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answered Apr 11 '17 at 15:17

BrodieG

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Can you somehow include an example? – Matthew Lundberg Apr 11 '17 at 19:15
@MatthewLundberg, done. Probably the best thing to do is look at the screencast or `demo('unitizer', package='unitizer')`. Also, is it a striking coincidence that your top QA is pretty much the script of my screencast, or did you see the screencast first and then came here (I had not seen your answer until I looked at your profile just now). – BrodieG Apr 11 '17 at 20:14
A complete coincidence, I assure you, and indeed it is a good one. – Matthew Lundberg Apr 11 '17 at 21:19

score 2 · Answer 2 · answered Mar 28 '17 at 23:10

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As of 2017, testthat has the feature expect_equal_to_reference, which does exactly what the question asks. I guess Hadley W. figured out a way.

answered Mar 28 '17 at 23:10

Yes indeed. I have been using it for a while. I had forgotten about this question. I'm also about to release [unitizer](https://github.com/brodieG/unitizer), which does this in a more comprehensive manner. – BrodieG Mar 29 '17 at 00:06

Testing Against Stored R Objects

2 Answers2